Mustard white butterfly, a North American native whose numbers are decreasing and which needs our protection. Photo: © Marian Bell Whitcomb
The following comment was submitted by reader Marian Whitcomb in response to the article Why You Should Think Twice Before Destroying Garden Caterpillars and Spiders, published on March 3, 2022. I thought it was so insightful that I wanted to share it more widely, with her permission, as a blog article.
We have been encouraged to believe “The only good bug is a dead bug” by marketers with products to sell and profits to make. Often insects that do significant damage to plants are those that have been introduced relatively recently to an area and reproduce out of control for lack of natural predators (such as birds, other bugs, and disease).
Knowing the difference between, say, a cabbage white butterfly (Pieris rapae), an invasive non-native species, and the mustard white butterfly (Pieris oleracea), a native species imperiled in much of its evolved range in North America, can help prevent extinction and protect the planet’s evolved biodiversity. In the case of both species, protective row covers for the Brassica species (cabbage, kale, broccoli, rutabaga, etc.) may be the best option for those of us growing these plants for food.
It is interesting to note the introduced invasive plant garlic mustard (Alliaria petiolate) is toxic to the larvae of the mustard white despite “smelling” right and attracting females to lay eggs on it.
I learned this by doing a “bioblitz” with the Nature Conservancy and discovering I had a yard FULL of the imperiled species that I had been thinking were the cabbage pests. By learning the scientific (Latin) name for the species, one can learn what is known about its life cycle and significance (to your local ecology and your vegetable crop) from expert researchers rather than idle speculators on social media.
You can get a great guide from the Entomological Society of America on where to look to find help in proper identification, hopefully before starting an eradication campaign. It is best to find actual experts, as many insects look similar to the naked eye (as the two above butterflies do until you know what to look for) and require years of training to accurately identify. Close-up and detailed photos are super helpful, but such technology is usually as close as the nearest cell phone these days. I recommend I-naturalist, as there are often entomologists lurking that who will personally help.
Help Birds, Limit Night Lights
It is important to add that controlling lights at night (going to motion sensors, yellow bulbs and pointing lights to specific places using “hats”) will literally do a “world” of good for the bird life in your yard as EACH species of 96% of songbirds relies on the larvae (caterpillars) of some 12,500 species of moths which die wholesale beating themselves to death on unnatural lights and windows rather than reproducing. Chickadees alone require literally thousands each time they reproduce.
Birds control insects and spread seeds in an ecology, and caterpillars feed them. Butterflies and moths provide pollination and other services poorly understood by most people.
A tiny fraction of these animals pose any threats to your sweaters or cabbages. For comparison, we have +-825 species of butterflies and +-4,000 species of bees native to North America. If you want to “save pollinators,” controlling night lights can be as important as planting food plants for them. Finding a good balance results in a rich array of life of all kinds in the garden AND a harvest for you too. What garden would be complete without the birds, butterflies (moths), and beetles, etc., that drive important ecological relationships and complete their cycles of life in an interdependent way?
Gardeners who take the time to learn about ecology can lead us to a healthier planet, and that is a very exciting idea. My husband and I see the results of our work in restoring habitat to support biodiversity every morning as we photograph wild birds most people never see at a feeder in our backyard over coffee. . . we don’t have to drive to a national park to find rare and fascinating native animals in their natural habitat, we incorporate consideration of the habitat needs of our neighbors in every gardening decision we make and are constantly learning.
About the Author
Marian Whitcomb is a retired zoo veterinary technician and garden designer who writes and shares her love of photography with her husband David Quimby in Nova Scotia. Both are serious students of ecology and the scientific work of Dr. Douglas Tallamy and the late Dr. E. O. Wilson.